11-13 week antenatal scan
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11-13 week antenatal scan is considered a routine investigation advised for the fetal well being as well as for early screening in pregnancy (see antenatal screening).
It includes multiple components and is highly dependant on the operator. Traditionally three factors are used to calculate the risk of trisomies:
-
crown rump length (must be 45 to 84 mm, gestation age 11 weeks
03 days to 13 weeks 6 days) - nuchal translucency
- fetal heart rate
Additional markers increase the detection rate and reduce the false positive rates:
- nasal bone
- ductus venosus flow
- tricuspid flow
Combining these factors with blood tests (i.e. dual marker) has been reported to achieve nearly 95% detection rate for trisomies.
Apart from the screening protocol, early detection of major anomalies may be possible and the checklist must include the following conditions:
- acrania
- encephalocele
- alobar holoprosencephaly
- iniencephaly
- body stalk deformity
- gastroschisis
- omphalocele
- limb reduction
- megacystis
See also
-<a href="/articles/crown-rump-length">crown rump length</a> (must be 45 to 84 mm, gestation age 11 weeks 0 days to 13 weeks 6 days)</li>- +<a href="/articles/crown-rump-length">crown rump length</a> (must be 45 to 84 mm, gestation age 11 weeks 3 days to 13 weeks 6 days)</li>
-</ul><h4>See also</h4><ul><li><a title="early structural scan" href="/articles/early-structural-scan">early structural scan</a></li></ul>- +</ul><h4>See also</h4><ul><li><a href="/articles/early-structural-scan">early structural scan</a></li></ul>
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